Industrial process waste streams such as dairy process streams are useful sources for the manufacture of sugars, in particular the manufacture of lactose. Whey, which is a watery liquid that separates from curd when milk is clotted, as in cheese making, contains valuable nutrients, including considerable amounts of lactose. Since lactose is a commercially important product particularly in the manufacture of infant milk-substitute formulas, confectionery, chocolate, baked goods, etc, several methods have been developed for its isolation from whey. Lactose also has important applications in the pharmaceutical industry particularly in tabletting and for dry powder inhalers.
To date, most methods for the production of refined edible or pharmaceutical grade lactose from whey involve more than one crystallisation step. Precipitation of lactose, however, is a relatively slow process and re-crystallisation increases both time and costs associated with production. Crude lactose α-monohydrate with an ash of 1% has recently been extracted from deproteinised whey using a water-ethanol one step crystallisation process (Yilmaz and Temiz, 1997, Milchwissenschaft 52 (11) p 629-631). However, lactose obtained by such a method remains unsuitable for most food applications which require an ash content of <0.3% (edible grade) or <0.2% (refined edible) and for pharmaceutical applications which require an ash content of <0.1%. Singh et al (1991, J Food Sci 56 (3) p. 777-788) disclose demineralisation of whey permeate using ion exchange resins followed by alcoholic crystallisation directly from the resulting solution. Although pharmaceutical grade lactose can be obtained using this method, the disadvantage of the method is that large columns of cation and anion exchange resins are required and the lactose is crystallized at pH 2.5 in 80% ethanol with stirring for 3 h. Further, this method requires regeneration of columns and disposal of the alkaline/salty regenerant, and involves an acid wash in which hydrochloric acid is commonly used. It is well known that hydrochloric acid is corrosive to the stainless steel used in equipment, such as tanks, centrifuges, pumps, etc. in which these methods are generally performed. Consequently, it would be desirable to have an alternative simple and economical process for the production of high purity lactose from a lower purity source.
It is an object of the present invention to provide a method of crystallisation of lactose and a product thereof which will overcome or substantially ameliorate at least some of the deficiencies of the prior art or provide a useful alternative.
The inclusion in this specification of references to prior art is not to be taken as an admission that the cited prior art, or any part thereof, comprises the common general knowledge of those skilled in the field of the invention.